1. Field of the Invention
The present invention relates to wrenching tools, such as wrenches, spanners, pliers, etc., and more particularly to such tools made of plastics, which are suitable for use in the vicinity of breakable ceramics, glasses or the like.
2. Discussion of the Prior Art
Main bodies of such tools have conventionally been made of steel, and plastic material has not been used for the main bodies for the reason that plastic is inferior to steel with respect to its mechanical properties, particularly with respect to its rigidity.
In some cases, plastics have been used as electrical insulation, or to provide better gripping. However, plastics have not been used in the main body portion of the tools, but only in the handle grip portion as a cover thereof. Tools entirely made of plastic have not been seen.
These plastic covered tools are frequently used when working on the piping for toilets, washrooms, bathrooms, etc., after construction of a house or building has been completed since the toilet bowls, washing bowls, etc., are in many cases made of ceramics, and the floors thereof are also made of ceramic tiles. If a steel tool is used for piping work involving ceramics, the tool may inadvertently hit against or be dropped on a ceramic member, and as a result the ceramic member might break. Repair of these broken ceramics requires much work, time and expense.
For example, a wrench used for twisting nuts and other similar elements usually consists of a main body (or fixed jaw) and a movable jaw engaged with the fixed jaw and movable in the axial direction of the main body. An example of such a conventional wrench is shown in FIG. 1, in which the fixed jaws 1 is made by forging, while the movable jaw 2 is made by casting. Since special mechanical care is not usually taken at the engaging portion 1a between the movable jaw 2, backlash frequently occurs there.
When plated nuts or nuts 4 made of soft metal, such as copper, brass, gun metal, etc., are used, the angle .theta. between the contact faces of the main body 1 and the movable jaw 2 becomes larger for .DELTA..theta. compared with the normal case. Since the wrench has more rigidity than the material of the nut to be wrenched, the nuts may be damaged.